1. Field of the Invention
The present invention relates to a washer for washing pulp, such as paper pulp, and, more particularly, to a washer in a fiber stock preparation system.
2. Description of the Related Art
Pulp, such as paper pulp, may be suspended in water and transported to a paper-making machine for the manufacture of a paper web. The pulp suspension is usually treated in various ways prior to being transported to the paper-making machine, such as by bleaching and washing of bleach and other chemicals from the suspension.
A fiber stock preparation system is used to prepare the fiber stock or fiber suspension which is used in the paper-making machine for the production of a fiber web such as paper. A pulp washer is used to wash effluents from the fiber suspension in the paper-making machine. A fiber suspension with a predetermined consistency is transported into the washer where effluents in the fiber suspension are typically separated from the fiber suspension through drainage via gravitational force and centrifugal forces. The fiber suspension is normally carried by a wire through the washer. One or more showers which extend across the width of the wire in a direction transverse to the running direction are used to jet a fluid against the fiber suspension which is used to dilute and wash the fiber suspension.
In a washer as described above, multiple showers are typically used to wash the fiber suspension at successive locations along the length of the washer. After the clean water is jetted onto the fiber suspension with each shower, the excess water in the fiber suspension drains through the wire and carries the effluents away from the fiber suspension. It is desirable to remove as much water as possible from the fiber suspension after each shower so that washing of the fiber suspension is maximized. Various structures using centrifugal force, gravitational force and/or pressure are known to dewater the fiber suspension.
What is needed in the art is a washer providing improved washing while occupying less physical space.
The present invention provides a washing system which effectively washes a fiber suspension and removes effluents therefrom, while at the same time providing a washing system occupying less physical space.
The invention comprises, in one form thereof, a washing system for washing a fiber suspension associated with a fiber stock preparation system, including a plurality of rolls and a porous fabric carried by the plurality of rolls in a closed loop. The closed loop includes a lower run defining a washing zone, with the porous fabric moving in a running direction through the washing zone. The porous fabric has an upper surface in the washing zone which carries the fiber suspension thereon. A headbox is positioned within the closed loop and above the porous fabric at an upstream end of the washing zone. The headbox discharges a fiber suspension to be washed onto the upper surface of the porous fabric. An accept removal device is positioned within the closed loop and above the porous fabric at a downstream end of the washing zone. A plurality of showers, each having an inlet, are positioned within the closed loop and above the porous fabric in the washing zone between the headbox and accept removal device. A plurality of dewatering elements are positioned below the fabric in the washing zone. Each dewatering element is configured for removing water from a bottom surface of the porous fabric. An effluent tank has a plurality of compartments, with each compartment having an inlet and an outlet. At least one outlet of the effluent tank is connected with a corresponding shower inlet. A plurality of drainage pans are positioned below the lower run of the porous fabric. Each drainage pan is associated with at least one dewatering element and has an outlet. Each drainage pan outlet is connected with a corresponding effluent tank inlet.
An advantage of the present invention is that the washing system effectively washes the fiber suspension, while at the same time providing a compact washing system which occupies less physical space.
Another advantage is that the dewatering elements may be configured as table rolls, foils, and/or foil rolls.